Method of joining wires, strands and cords

ABSTRACT

This invention contemplates a method of forming a wire strand or cable comprising joining together two wires each having a diameter in the range of 0.10 to 0.30 millimeters by holding said wires fast with respect to one another at two spaced locations and twisting the wires between said locations so as to form a joined or spliced wire, stranding at least one such joined wire with additional wires so as to form a strand, and cabling at least one such strand with additional strands to form a cable. Also, the disclosure relates to the strand or cable thus produced which are particularly useful in reinforcing rubber or plastic material.

United States Patent Spiessens Sept. 30, 1975 METHOD OF JOINING WIRES, STRANDS 1,978,164 10 1934 Van lnwagen 6t al. 29/461 AND CORDS 2,454,417 l1/l948 I Zerr 57/142 2,646,298 7/1953 Leary 289/12 Inventor! Roger splessens, Dentcrgem, 2,796,662 6/1957 Saum 140/118 Belgium [73] Assigneez v Bekaert SA" Zwevcgem Primary E.\-aminerLowell A. Larson Belgium Attorney, Agent, or Firm-Shlesinger, Arkwright,

Garvey 8L Dinsmore [22] Filed: Nov. 30, 1973 [2]] Appl. No.: 420,618 [57] ABSTRACT This invention contemplates a method of forming a 30 Foreign A li ati priority m wire strand or cable comprising joining together two J, i l 197 U d d N 2640 73 wires each havmg a diameter 1n the range of 0.10 to 8 3 m 6 mg om 0.30 mllllmeters by holding said wires fast with respect [52] Us Cl 140/111, 57/142, 57/159 to one another at two spaced locations and twisting [5 l 1 Int Cl BZIF 7/00 the wires between said locations so as to form a joined [58] of 1 18 120 or spliced wire, stranding at least one such joined wire 140/122, 5 22 289/l 1 with additional wires so as to form a strand, and ca- 5 bling at least one such strand with additional strands to form a cable. Also, the disclosure relates to the [56] References Cited strand or cable thus produced which are particularly useful in reinforcing rubber or plastic material.

13 Claims, 4 Drawing Figures U.S. Patent Sept. 30,1975

FIG.I.

METHOD OF JOINING WIRES, STRANDS AND CORDS This invention relates to a method of joining wires, strands and cords and, more particularly, is concerned with a method of joining wires having a diameter in the range of from 0.10 to 0.30 mm, such wires being commonly used to form strands for use in metal cords, and a method of joining cords and strands comprising wires of said diameter.

Metal cords are used in the manufacture of reinforced articles of natural or synthetic rubber or plastics material, for example pneumatic tyres and hoses. Particulaly in the case of pneumatic tyres the cords should be extremely flexible and should be capable of undergoing repeated deformation and successive flexing without undergoing permanent deformation. These properties are obtained by constructing the cord of several strands, each strand comprising typically 2 to 7 wires each having a diameter in the range of from 0.10

' to 0.30 mm. The term wire is used herein to describe wire having a diameter in the range of from 0.10 to 0.30 mm.

In order to improve adhesion between the cords and the rubber of a tyre, each wire in the cord, which wire is typically made of steel, can be coated with, for exam ple brass.

The wires are generally made by a drawing operation and are stored on bobbins. Because the wires are so thin they periodically break during drawing. Up to now there has been no practical method known for joining together lengths of wire to obtain a satisfactory joint. Because of this it is necessary for strands to be made from unbroken lengths of wire. To minimise wastage, when a wire breaks the unbroken wire on the bobbin is placed in a group of bobbins having approximately the same length of unbroken wire thereon. Typically one group would contain bobbins having 1,000 to 2,000 meters of unbroken wire, another group would contain bobbins having 2,000 to 3000 meters of unbroken wire, etc. Subsequently bobbins from the same group are mounted on a twisting machine and a strand is twisted. The length of the strand is determined by the shortest wire and hence wastage occurs.

In order to avoid the time consuming process of classifying the bobbins and the wastage inherent in the system described, it has been proposed to weld together the free ends of a broken wire. This proposal has not met commercial acceptance since not only is the welding operation time consuming but the breaking stress of the joint is produced with currently available equipment is usually less than 50% of the ultimate tensile stress (breaking stress) of the unbroken wire. Furthermore, the welding operation removes the brass coating which coating is very desirable when the wire is to be used in cords for pneumatic tyres.

One aspect of the present invention provides a method of joining two wires each having a diameter in the range 0.10 to 0.30 mm, which method comprises the steps of arranging the wires along one another, holding said wires fast with respect to one another at two spaced locations, and twisting said wires between said locations.

We have found that this method is particularly suitable for joining wires having a diameter in the range of from 0.15 to 0.25 mm.

The wires are preferably twisted between 3 and 4 complete turns and the holding locations are preferably spaced in the range 15 to 24 mm apart, advantageously 19 mm apart.

Another aspect of the present invention provides a method of joining two cords or strands each having wires with a diameter in the range 0.10 to 0.30 mm, which method comprises the steps of arranging the cords or strands alongside one another, holding said cords or strands fast with respect to one another at two spaced locations, and twisting said cords or strands between said locations.

The cords or strands are preferably twisted between 3 and 4 complete turns and the holding locations are preferably spaced not less than 19 mm apart, advantageously 30 mm apart.

The present invention also provides wires, cords and strands when joined by a method in accordance with the invention.

We have found that under favourable conditions the ultimate tensile strength of a wire with a joint in accordance with the invention is only 22 to 32% lowerthan that of the unbroken wire. Furthermore, the method of the invention does not cause an undesirable degree of removal of brass from the surface of a wire compared with the welding operation hereinbefore described.

One embodiment of a joint in accordance with the invention will now be described by way of example and with reference to the accompanying drawing in which:

FIG. 1 shows, on an enlarged scale, two wires about to be joined together;

FIG. 2 shows the wires joined together;

FIG. 3 shows a perspective view of a cord comprising several strands one of which strands includes a wire comprising two lengths joined together; and

FIG. 4 shows a tool for use in joining the wires.

Referring to FIGS. 1 and 2 of the drawing, two wires 1 and 2 are laid side-by-side with their free ends 3 and 4 facing away from one another. the wires 1 and 2 respectively are held fast at two holding locations a distance L apart and the two wires are twisted (FIG. 2) at 5 which is midway between'the two locations. The free ends 3 and 4 of wires 1 and 2 are then wrested off close to the joint as shown in FIG. 2. It is preferable to wrest of the free ends of the wires, as at 6, in a direction whereby the twisting connection is strengthened.

Referring now to FIGQ4, there is shown a tool 10 which is suitable for twisting the wires 1 and 2. The tool 10 comprises a circular disc having a wedge-shaped opening 11 therein. In use, the wires 1 and 2 are placed in the opening 11 and the disc is rotated to twist the wires 1 and 2. Another suitable tool is disclosed in US. Pat. No. 3,650,302.

The number of turns of the wires 1 and 2 necessary to effect a satisfactory joint depend inter alia on the diameter of the wire to be connected and the desired tensioning of the wires. If the disc is rotated too many times the wires 1 and 2 will break whereas insufficient rotation of the wires will allow the wires 1 and 2 to slip relative to one another. V

Referring now to Table l, the ultimate tensile stress (breaking stress) of wires of various diameters is correlated with the breaking stress of the same wires when joined with 2, 3, 4 and 5 twists. To provide a ready comparison betwen the results the breaking stress of each unbroken wire is designated as and the breaking stress of various joints formed from that wire are expressed in both their absolute magnitude and the percentage of strength of the unbroken wire. All the figures given are the mean of five tests, and the overall length L (see HO. 2) of each joint was in the range 15 values given for the cords using unbroken wires are the mean of tests whereas the values given for the cords using joined lengths of wire are the mean of tests. It is noted that the variation of breaking stress in the latto mm. 5 ter case was much greater than that in the first case. It

TABLE 1 Breaking stress( kg) Wire diameter without 2 turns 3 turns 4 turns 5 turns mm connection twisted twisted twisted twisted 0,15 5,07 100% 1,89 37% 3,44 68% 3,46 (68%) 3,024 61% 0,175 6,5 100% 2,4 37% 4,66 72% 4,314 67% 3,76 57%. 0,20 8,4 100% 3,29 39% 6,01 72% 5,7 68% 5,49 65% 0,22 9,00 (100% 5,46 (61%) 7,04 (78%) 6,84 (76%) 6,6 73%) 0,25 ll,00 (100%) 7,24 (68%) 7,82 (7l7r) wire is wire is broken broken It will be seen from Table 1 that the maximum breakis also noted that each wire in the cords comprising ing stress for each wire tested occurs with either 3 or joined length of wire contained joins at random inter- 4 turns, and that this stress is only 22 to 32% lower than ValS. that f the unbroken wlre QSFOmPaYeQWIIh of 20 It will be seen that in all cases the breaking stress of the pnor art welded connecnon The Wlth a the cords containing joined lengths of wire is less than etejr of greater than mm broke after bemg that of the equivalent cord containing unbroken twjsted 4 nmes' subseqjlejm tests wlth a strandmg lengths of wire. In all but one case the percentage dec hme {lave that It prefefred use a crease in breaking stress was less than or equal to 5% non with four twistswhere possible since there is less 25 and in one Case as low as likelihood of such a oint hitching in the stranding machine compared with a joint having three twists. 2 Diameter of the Cords To test the properties of the joined lengths of wire in various measurements were made to compare the Strands and cords a mulupllclty of wires broken diameter of cords using wires without joints and the and joined at intervals of 200 meters. These wires were maximum diameter of Wires with joints The results are f 22 s F iz z 123 ;3 :3312: set out in Table III from which it will be seen that the C 6 wires w re dr mg 0 J n percentage increase in diameter of the cords for the occurred at the same place in the cable. Subsequently Cords tested was in the ran 6 of 7 to 9% the strands were used in a cording operation to form g cords. It was found that the greatest number of ruptures TABLE I took place during the stranding operation and it was believed that this was due to the fact that each wire is independtly subjected to tensile stress during the Construction Diameter (rnm) Diameter (mm) crease stranding operation. ln contrast, during the cording op- (mm) 1mmS eration each joint is strengthened by the surrounding 40 7 X 3 X (H5 097 L06 9 wires in its strand. During applicants tests only 1 joint 1 3 5x7) 128 1,37 7 in 100 failed during the stranding operation and less 522 1 I 56 I 68 8 than 1 joint in 400 failed during the cording operations. 7 X 3 X ():2() 1 Q 9 The cords formed were then tested as follows:

l. Tensile test for determining Ultimate Tensile Stress In Order to improve the appearance of a cord com (Breakmg Stress)" tainingjoined lengths of wire, it is preferable to arrange for the joined wires to form the core of the strands and, .Cords of dlffermg Constructlons with and.wlthol.lt where appropriate, for these strands to form the core oined lengths of wire were tested to determine their of a cord However if the Strand or cord is made of l r out TallI.T breakmg Stress The resu ts a 8 Set m b 6 he many wires then any oint occurring at the periphery of the strand or cord is very difficult to see. FIG. 3 shows TABLE I] such a situation.

Construction Num- Breaking Breaking Breaking Various tests were carried out to find out what effect ber i (mm) of Stress stress Stress the lengh L of the oint has on the ultimate tensile turns without with decrease strength of the oint. These results are set out in Table ai i g? (79) IV. The column headed OT contains the ultimate ten- I IO 5 g n g sile stress oflengths of oin free wire whereas those col- 7 x 3 x 0,15 3 99 94 5 umns headed 2T, 3T and 4T respectively designate i fi g fg 4 I00 96 7 3 3 lengths of wires joined by two, three and four twists re- (IX3) (5X7) 3 184 8 spectively. Each of the columns headed 2T, ST and 4T is subdivided into 3 columns headed by the length L of g z g gi g 52: the joint. The superscripts b and s respectively denote 7 x 7 x 0,17 4 262 257 2 failure of the joint by rupture of the wire at one end of 7 3 0,20 3 167 156 5.6 1 7 X 3 X 020 4 167 152 10 the oint, and slipping of the wires of the oint relative to one another.

' TABLE IV 1 3 Tensile force (kg) Number 4 of turns T 2T 3T 4T or twlst- 1 ings 1 Length L mm 19 mm 24 mm 15 mm 19 mm 24 mm 15mm 19 mm 24 mm Reason for rupture ":rupture of the connection at one of the ends ':shifting of the two broken ends from each other As can be seen from Table IV, a joint of length19' for wires having a diameter of 0.22 and 0.30 mm. In all these cases the joint had a strength in the range 7077.6% of the unbroken wire. Although wires having 3 turns and ajoint length of 19 mm with a diameter less than 0.20 mm proved satisfactory for forming strands, wires so joined with a diameter of greater than 0.20 tended to hitch during the stranding operation. This problem was reduced by increasing the length of the joint to 24 mm.

It is proposed to use the method of the invention for joining lengths of wire used to bind metal cords or strands together. The wire is wound in a spiral around a group of substantially parallel cords and strands. theretofore, when the wire broke it was customary to Applicants have also found that, the method of joining together lengthsof wire as hereinbefore described is suitable for joining the ends of a broken strand com- 25 prising wires having a diameterin the range 0.10 0.30

mm and for joining theends of a thin broken cord comprising strands each formed from wires having a diameter in the range 0.10 0.30 mm. It is to be noted that in these cases each wire is not individually connected to an adjacent wire but that one strand or cord end is connected directly to another strand or cord end respectively. Applicants have found that for joining lengths of strands the length L of the joint should not be less than 19 mm and that the strands should consist -of a maximum of 5 wires. The tensile strength of as in Table IV.

TABLE V Tensile force (kg) Number of turns or twistings OT 2T 4 1 3T 4T Length L 19 mm 25 mm 30 mm 19 mm 25 mm 30 mm 19 mm 25 mm mm strand constructions 5,7 4,8 2,5 9,2 9,5 9,3 9,9 2 X 0,175 13 s s s b b s b 10,2 8 5,9 13,2 13,2 14,4 14,2 2 X 0,22 18,9 5 s s b b s b 3,9 2,9 1,5 8,3 6,8 6,23 8,8 9.7 3 X 0,15 14,9 5 s s s s s s b 9,7 9,8 6,31 17,4 17,9 18,1, 16,5 19,1 3 X 0,20 28,6 s s s s s s b b 7,3 5,7 2,4 11,1 9,2 9,3 11,3 11,1 4 X 0,175 28,1 s s s s s s s s Reason of rupture rupture of the connection at one of the ends 6. shifting of the two broken ends from each other.

pass the broken captive end of the wire through the cord or strand and to pass the free end of the wire through the cord or strand alongside the captive end before recommencing winding. It will be seen that the method of the present invention provides a more satisfactory solution to the problem of binding.

Three different cords were formed with their core strand formed from joined lengths of strand The con- 65 struction of the cords was as follows.

(3 X015) +(5 X 7 X 0.15) 1 with a length of 1,000 m. The core strand (3 X 0.15) was provided with 30 joints. No ruptures occurred during the cording operatron.

(7 X 4 X 0.175): The core strand (4 X 0.175) was provided with 25 joints. No ruptures occurred during the cording operation.

(3 X 0.20) (6 X 0.35) with a length of 1,000 m. The core strand (3 X 0.20) was provided with 30joints. No ruptures occurred during the cording operation What we claim is 1. A method of forming a wire strand comprising:

a. joining two wires each having a diameter in the range of 0.10 to 0.30 mm by l. holding said wires fast with respect to one an- I other at two spaced locations, and 2. twisting said wires at least two complete turns between said locations so as to form a joined wire, b. stranding at least one such joined wire with other wires to form a strand. 2. A method according to claim 1 wherein saidjoined wire comprises the core wire of said strand.

3. A method according to claim 1, wherein said wires have a diameter in the range 0.15 to 0.25 mm.

4. A method according to claim 1, wherein the said wires are twisted between 3 and 4 complete turns.

5. A method according to claim 1, wherein said holding locations are spaced in the range to 24 mm apart.

6. A method according to claim 5, wherein said holding locations are spaced 19 mm apart.

7. A strand produced by the method of claim 1.

8. A method of forming a cable comprising:

a. joining two cords or strands each formed of wires having a diameter in the range of 0. 10 mm to 0.30 mm by l. arranging said cords or strands alongside one another,

2. holding said cords or strands fast with respect to one another at two spaced locations and,

3. twisting said cords or strands at least two complete turns between said locations to form a joined cord or strand, and

b. cabling at least one suchjoined cord or strand with other cords or strands to form a cable.

9. A method according to claim 8 wherein said joined cord or strand comprises the core wire of said cable.

10. A method according to calim 8, wherein the said cords or strands are twisted between 3 and 4 complete turns.

11. A method according to claim 8, wherein said holding locations are spaced not less than 19 mm apart.

12. A method according to claim 11, wherein said holding locations are spaced 30 mm apart.

13. A cable produced by the method of claim 8. 

1. A method of forming a wire strand comprising: a. joining two wires each having a diameter in the range of 0.10 to 0.30 mm by
 1. holding said wires fast with respect to one another at two spaced locations, and
 2. twisting said wires at least two complete turns between said locations so as to form a joined wire, b. stranding at least one such joined wire with other wires to form a strand.
 2. A method according to claim 1 wherein said joined wire comprises the core wire of said strand.
 2. twisting said wires at least two complete turns between said locations so as to form a joined wire, b. stranding at least one such joined wire with other wires to form a strand.
 2. holding said cords or strands fast with respect to one another at two spaced locations and,
 3. twisting said cords or strands at least two complete turns between said locations to form a joined cord or strand, and b. cabling at least one such joined cord or strand with other cords or strands to form a cable.
 3. A method according to claim 1, wherein said wires have a diameter in the range 0.15 to 0.25 mm.
 4. A method according to claim 1, wherein the said wires are twisted between 3 and 4 complete turns.
 5. A method according to claim 1, wherein said holding locations are spaced in the range 15 to 24 mm apart.
 6. A method according to claim 5, wherein said holding locations are spaced 19 mm apart.
 7. A strand produced by the method of claim
 1. 8. A method of forming a cable comprising: a. joining two cords or strands each formed of wires having a diameter in the range of 0.10 mm to 0.30 mm by
 9. A method according to claim 8 wherein said joined cord or strand comprises the core wire of said cable.
 10. A method according to calim 8, wherein the said cords or strands are twisted between 3 and 4 complete turns.
 11. A method according to claim 8, wherein said holding locations are spaced not less than 19 mm apart.
 12. A method according to claim 11, wherein said holding locations are spaced 30 mm apart.
 13. A cable produced by the method of claim
 8. 